RF instruments for measuring the voltage standing wave ratio (“Γ”) of a cable are known in the art.
The standing wave ratio (“Γ”) is given by:Γ=A/R 
where “A” is the reflected signal and “R” is the incident signal. Both the signals “A” and “R” are vectors. Ideally, at one particular frequency point for a given device under test, the ratio “A/R” will have a fixed magnitude and a fixed angle.
In some test setups, however, there may be unwanted interference. The unwanted interference may affect the accuracy of the Γ measurement. Due to the interference, the Γ measurement may vary with time even at a fixed frequency of the RF source for the Γ measurement. It would be desirable to be able to remove this unwanted interference from the measurement to provide an accurate measurement of Γ.